Process of preparing hydroxythionaphthenes



Patented D e-c123, i930 UNETED STATES PATENT OFFICE ERWIN HOFFA AND FRITZ MILLER, 01? FRANKFURT-ON-THE-MAI1\T-HOCHST, GER- MANY, ASSIGNORS TO GENERAL ANILINE WORKS, INC., OF NEW YORK, N. Y., A

CORPORATION DELAVTARE PROCESS OF PREPARING HYDBOXYTI-IIOITAPHTHENES No Drawing. Application filed August 2, 1928, Serial No. 297,102, and in Germany August 17, 1927.

wherein R stands for an unsubstituted or substituted aromatic residue.

It had been assumed that the arylcarboXyL ic acid amide-o-rtho-thioglycollic acids would be formed as intermediary products during the transformation of cyanoaryl-ortho-thioglycollic acids into aminothionaphthenecarboXylic acids. proved to be erroneous since it has been as- 'certained that by the action of alkali the arylcarboxylic acid amide-ortho-thioglycollic acids are not converted into aminothionaphthenecarboxylic acids but into hydroxythionaphthenecarboxylic acids (cf. the co-pending U. S. patent application Ser. No. 211,352 filed by Erwin Hoffa, Jens Muller and Fritz Muller on August 9, 1927).

We have now found that the preparation of arylcarboxylic acid amide-ortho-thioglycollic acidsfrom cyanoaryl-ortho-thioglycollic acids can also be effected in an alkaline solution by causing hydrogen peroxide to act upon such solutions. The saponification of nltriles by means of alkali and hydrogen peroxide is as 'such known and described for instance in Journal fiir Praktische Chemie volume 93, page 137. It was, however, not to be foreseen that this process could also be applied to the above-described purpose; as it has been known that by the action of an alkali cyanoarylorthothioglycollic acids are transformed into aminothionaphthenecarboxylic acids.

Apart from the chemical novelty of the process it afiords considerable technical advantages. Tt is no longer necessary to isolate This view has, however,.

the resulting arylcarboxylic acid amide-on tho-thioglycollic acid which can now be transformed into the hydroxythionaphthene in the same solution in which it has been formed, by a further alkaline treatment according to the process described in the U. S. application Ser. No. 211,852 above referred to. Thus a way has been found for preparing hydroxythionaphthenes from cyanoaryl-ortho-thioglycollic acids in a technically simple man ner and in a single operation.

The following examples illustrate our invention, but they are not intended to limit it thereto. The parts are by Weight:

1. 23.7 parts of 2-cyano-5-ethoxybenzenel-thioglycollic acid are dissolved in a solution of 8 parts of caustic soda in 100 parts of water while heating to 410 C. and to this solution are added 100 parts of a 8% solution of hydrogen perioxide. The mixture is further heated, another 100 parts of a 3% solution of hydrogen peroxide being gradually run in. The temperature is raised to 70 C. and maintained there for some time. By acidifying the solution, the carboxylic acid amiglle which has been formed can be precipitate The reaction takes place according to the following equation:

However, when carrying out the reaction for the purpose of forming the hydroxythionaphthene, one may dispense with the isolation of the carboxylic acid amide. 8 parts of caustic soda are added to the solution and the whole is heated to 95 C. for 6 to 7 hours in the manner described in the afore-mentioned U. S. application Ser. No. 211,852, until the evolution of ammonia has ceased. The solu-v tion is then acidified and the resulting 6-ethoXy-hydroxythionaphthene is filtered by suction.

C. and the mixture is heated to C.

for 1 hours. The solution is then quickly heated to 7 0 (1., parts of a 3% solution of hydrogen peroxide being added thereto at C. and another 50 parts at C. At 70 C. there is then introduced in the course of half an hour a further quantity of 100 parts of a 3% solution of hydrogen peroxide and after the evolution of oxygen has decreased, the whole is acidified with hydrochloric acid. filtered by suction and washed with a small quantity of water and then with ether. It is the 2-carboxylic acid amide of l-methylbenzene-5-chloro-8-thioglycollic acid-2-carboxylic acid, melting at 17 2 C.

We claim:

1. The process of preparing hydroxythionaphthenes which consists in saponifying a cyanoaryl-ortho-thioglycollic acid of the for mula wherein R stands for an unsubstituted or substituted aromatic hydrocarbon residue, by the action of hydrogen peroxide in an alkaline solution so as to form the corresponding arylcarboxylic acid-amide-ortho-thioglycollic acid of the formula:

' -CO.NH2

wherein R stands for an unsubstituted or sub.- stituted aromatic hydrocarbon residue, by the action of hydrogen peroxide in an alkaline solution so as to form the corresponding arylcarboxlic acid-amide-ortho-thioglycollic acid of the formula:

' CO.NH2

.= S.OH2.GOOH

wherein R stands for an unsubstituted or substituted aromatic hydrocarbon residue, and

. transforming the latter by the further action The product of the reaction is ponifying 5 -ethoxy 2 cyanobenzene-I-thioglycollic acid by the action of hydrogen peroxide in an alkaline solution as to form 5-etl1oxy-benzene-2-carboxylic acid amide-1- thioglycollic acid and transforming the latter by the action of an alkali into the 6-ethoxyhydroxythionaphthene.

4. The process of preparing -6-ethoxyhydroxythionaphthenewhich consists in saponifyingat a temperature of between 40 C. and 70 C. 5-ethoxy-2-cyanobenzene-l-thioglycollic acid by the actionof hydrogen peroxide in an alkaline solution so as to form 5-ethoxybenzene-2-carboxylic acid amide-l-thioglycollic acid and transforming the latter by the action of an alkali into the 6-ethoxyhydroxythionaphthene.

In testimony whereof, we affix our signatures.

'ERWIN HOFFA.

FRITZ MULLER. 

